Ultraviolet A 10344-23 out of 5

Problem I

23 out of 5

Input:
Standard Input

Output:
Standard output

Time limit:1 second

Memory limit:
32 MB

Your task is to write a program that can decide whether you can find an arithmetic expression consisting of five given numbers
(1 <= I <= 5) that will yield the value 23.
For this problem we will only consider arithmetic expressions of the following from:

where : {1,2,3,4,5} -> {1,2,3,4,5} is a bijective function

and  {+,-,*} (1<=i<=4)

Input

The input consists of 5-tupels of positive integers, each between 1 and 50.
Input is terminated by a line containing five zero's. This line shoshould not be processed.

Output

For each 5-tupel print "possible" (without quotes) if their exists an arithmetic expression (as described abve) that yields 23. Otherwise print "impossible ".

Sample Input

1 1 1 1 1

1 2 3 4 5

2 3 5 7 11

0 0 0 0 0

Sample output

Impossible

Possible

Possible

. At the beginning of recursion, each time a number is lifted without a symbol, and then the current number is combined with the symbol of the previous number before the operation, so that I am confused .....

Put the number and symbol in the list first, and then calculate the number and symbol in the list again, 5! * 3 ^ 4 scale

#include<stdio.h>#include<string.h>int f,visit[10],a[10],b[10];int sort(int n,int num){int i; if ((n==5)&&(num==23)) f=1; if ((n>=5)||(f)) return 0; for (i=1;i<=5;i++) if (visit[i]==0) {visit[i]=1;  sort(n+1,num+a[i]);  sort(n+1,num-a[i]);  sort(n+1,num*a[i]);  visit[i]=0; }}int main(){int i; while (scanf("%d",&a[1])) {  for (i=2;i<=5;i++)  scanf("%d",&a[i]);  if ((a[1]==0)&&(a[2]==0)&&(a[3]==0)&&(a[4]==0)&&(a[5]==0)) break;  memset(visit,0,sizeof(visit));  memset(b,0,sizeof(b));  f=0;  for (i=1;i<=5;i++)  {visit[i]=1;   sort(1,a[i]);   visit[i]=0;  }  if (f) printf("Possible\n");    else printf("Impossible\n"); } return 0;}